全文获取类型
收费全文 | 12223篇 |
免费 | 381篇 |
国内免费 | 281篇 |
专业分类
电工技术 | 249篇 |
综合类 | 600篇 |
化学工业 | 1705篇 |
金属工艺 | 1212篇 |
机械仪表 | 1359篇 |
建筑科学 | 862篇 |
矿业工程 | 831篇 |
能源动力 | 1188篇 |
轻工业 | 71篇 |
水利工程 | 128篇 |
石油天然气 | 349篇 |
武器工业 | 137篇 |
无线电 | 473篇 |
一般工业技术 | 1562篇 |
冶金工业 | 673篇 |
原子能技术 | 214篇 |
自动化技术 | 1272篇 |
出版年
2024年 | 17篇 |
2023年 | 176篇 |
2022年 | 367篇 |
2021年 | 302篇 |
2020年 | 333篇 |
2019年 | 294篇 |
2018年 | 307篇 |
2017年 | 343篇 |
2016年 | 394篇 |
2015年 | 431篇 |
2014年 | 667篇 |
2013年 | 691篇 |
2012年 | 630篇 |
2011年 | 1011篇 |
2010年 | 638篇 |
2009年 | 755篇 |
2008年 | 669篇 |
2007年 | 765篇 |
2006年 | 713篇 |
2005年 | 613篇 |
2004年 | 486篇 |
2003年 | 388篇 |
2002年 | 346篇 |
2001年 | 232篇 |
2000年 | 187篇 |
1999年 | 195篇 |
1998年 | 174篇 |
1997年 | 125篇 |
1996年 | 123篇 |
1995年 | 108篇 |
1994年 | 66篇 |
1993年 | 64篇 |
1992年 | 54篇 |
1991年 | 45篇 |
1990年 | 29篇 |
1989年 | 33篇 |
1988年 | 30篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1963年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
Massimo Corcione 《International Journal of Heat and Mass Transfer》2005,48(17):3660-3673
Steady laminar free convection from flat vertical arrays of equally-spaced, horizontal isothermal cylinders set in free air, is studied numerically. A specifically developed computer-code based on the SIMPLE-C algorithm is used for the solution of the mass, momentum and energy transfer governing equations. Simulations are performed for arrays of 2-6 circular cylinders, for center-to-center separation distances from 2 up to more than 50 cylinder-diameters, and for values of the Rayleigh number based on the cylinder-diameter in the range between 5 × 102 and 5 × 105. It is found that the heat transfer rate at the bottom cylinder remains the same as a single cylinder. In contrast, the downstream cylinders may exhibit either enhanced or reduced Nusselt numbers depending on their location in the array and on the geometry of the array. Heat transfer dimensionless correlating equations are proposed both for any individual cylinder in the array and for the whole tube-array. New correlation-equations for the calculation of the heat transfer rate from a single cylinder to the surrounding air are also proposed and compared to those available in the open literature. 相似文献
112.
Amaresh Dalal Manab Kumar Das 《International Journal of Heat and Mass Transfer》2005,48(14):2986-3007
Natural convection in two-dimensional enclosure with three flat and one wavy walls is numerically investigated. One wall is having a sinusoidal temperature profile. Other three walls including the wavy wall are maintained at constant cold temperature. This problem is solved by SIMPLE algorithm with deferred QUICK scheme in curvilinear co-ordinates. The tests were carried out for different inclination angles, amplitudes and Rayleigh numbers while the Prandtl number was kept constant. The geometrical configurations considered were namely one, two and three undulations.The results obtained show that the angle of inclination affects the flow and heat transfer rate in the cavity. With increase in amplitude, the average Nusselt number on the wavy wall is appreciably high at low Rayleigh number. Increasing the number of undulations beyond two is not beneficial. The trend of local Nusselt number is wavy. 相似文献
113.
D. Bouris E. Konstantinidis D. Castiglia 《International Journal of Heat and Mass Transfer》2005,48(18):3817-3832
This paper describes an integrated approach into the design and evaluation of a novel tube bundle heat exchanger that achieves higher heat transfer levels at lower levels of pressure drop, while remaining less susceptible to gas-side fouling. The approach combines laboratory scale experiments with industrial observations and numerical simulations of full-scale heat exchangers to study the thermal, hydraulic and fouling characteristics of tube bundle heat exchangers. Three arrangements are compared and the advantages of the proposed novel arrangement are demonstrated. Enhanced heat transfer rates are combined with reduced pressure drop and gas-side fouling rates through careful design of the shape of the tube cross-section and reduced transverse spacing. 相似文献
114.
This study presents a methodology to assess suitability of a site for small scale concentrated solar power (CSP) systems for its energy conversion efficiency and make‐up water requirement. Energy conversion efficiency of CSPs relies not only on the level of direct solar radiation but also on the performance of the cooling system. Regions with high solar potential have to deal with heat rejection at elevated temperatures which causes reduced energy conversion efficiencies due to high condenser temperatures. It is desirable to utilize wet cooling systems as they can achieve temperatures lower than the dry bulb temperature by evaporative cooling. On the other hand, such regions usually lack water resources which deteriorate the sustainable nature of CSP applications. This study combines various available models for both solar resource estimation and cooling systems' performance considering (i) the influence of ambient temperatures, and (ii) the influence of humidity levels. These models are integrated together to analyze the use of dry or wet cooling systems in terms of overall energy output and water consumption at a selected site in northern Cyprus. The model inputs consist of only annual hourly surface weather data and the location of the site of interest. The results show that dry cooling unit at northern Cyprus is capable of saving water about 18.7 ton/MWh while it produces 27% less energy compared to the wet cooling alternative for the representative annual weather data. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
115.
116.
117.
118.
119.
120.